

CYSTINE. 177 



CYSTINE. C 6 H 6 NS 2 O 4 . 

 Chemical Relations. 



Properties. This body occurs in colourless, transparent, hexa- 

 gonal plates or prisms, is devoid of taste and smell, and is insoluble 

 in water and alcohol ; it dissolves in oxalic acid and in the mineral 

 acids, forming with them saline combinations, most of which are 

 crystallisable, but it does not unite with acetic, tartaric, or citric acid : 

 it is decomposed by nitric acid, leaving, on the evaporation of the 

 fluid, a reddish brown mass ; it dissolves freely in the caustic fixed 

 alkalies and their carbonates. It dissolves in caustic ammonia, but 

 does not unite with it, so that on evaporation it crystallises un- 

 changed. It is insoluble in carbonate of ammonia ; hence it is best 

 precipitated from its acid solutions by carbonate of ammonia, and 

 from its alkaline solutions by acetic acid. 



Cystine does not fuse on the application of heat, but it burns 

 with a bluish green flame, developing at the same time a very pecu- 

 liar acid odour ; on dry distillation it developes a stinking empy- 

 reuma and ammonia, and leaves a voluminous porous coal. On 

 boiling it with alkalies, ammonia is first developed, and subsequently 

 an easily inflammable gas, which burns with a blue flame. 



Composition. Cystine has been analysed by Prout, Baudri- 

 mont, Thaulow,* and Marchand,f with perfectly identical results, 

 yielding the above formula, according to which this substance 

 contains : 



Carbon 6 atoms .... SO'OOO 



Hydrogen .... 6 .... 5-000 



Nitrogen 1 .... 11 '606 



Sulphur 2 .... 2'667 



Oxygen 4 26'667 



100-000 



Its atomic weight=1336'0. 



Since cystine, which has also received the name of cystic oxide, 

 unites with certain acids to form crystalline salts, Berzelius classi- 

 fies this body with the combinations of conjugated ammonia 

 = H 3 N.C 6 H 3 S 2 O 4 . If, however, this view be correct, much is still 

 wanting for the establishment of the rational formula of cystine, for 



* Ann. d. Ch. u. Pharm. Bd. 27, S. 197. 

 t Journ. f. pr. Ch. Bd. 10, S. 15-18. 



N 



